Vitaros,

http://www.hmdb.ca/metabolites/HMDB0001442
http://www.genome.jp/dbget-bin/www_bget?drug:D00180
http://www.genome.jp/dbget-bin/www_bget?cpd:C04741
https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=149351
https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?sid=46508029
https://www.chemspider.com/Chemical-Structure.4444306.html
http://www.bindingdb.org/bind/chemsearch/marvin/MolStructure.jsp?monomerid=50101853
https://mor.nlm.nih.gov/RxNav/search?searchBy=RXCUI&searchTerm=598
https://www.ebi.ac.uk/chebi/searchId.do?chebiId=15544
https://www.ebi.ac.uk/chembldb/index.php/compound/inspect/CHEMBL495
https://zinc.docking.org/substances/ZINC000003813088
http://bidd.nus.edu.sg/group/cjttd/ZFTTDDRUG.asp?ID=DAP001490
http://www.pharmgkb.org/drug/PA448334
http://www.guidetopharmacology.org/GRAC/LigandDisplayForward?ligandId=1882
https://www.ebi.ac.uk/pdbe-srv/pdbechem/chemicalCompound/show/XPG
http://www.rxlist.com/cgi/generic/alprostadil.htm
https://www.drugs.com/cdi/alprostadil.html
http://www.pdrhealth.com/drug_info/rxdrugprofiles/drugs/cav1073.shtml
https://en.wikipedia.org/wiki/Prostaglandin_E1